The present invention relates generally to monitoring annunciator devices, and, in particular to a monitoring annunciator apparatus for monitoring the status of field contact points through the use of a single wire pair for each monitored contact point so as to provide separate audible and visual indication of both the occurrence of a change in status of each monitored field contact point and the occurrence of a change in the integrity of each wire pair connecting each contact point to the apparatus.
Over the years, a number of apparata have been addressed to the centralized monitoring of remotely positioned alarm contacts in order to permit a control room operator to visually scan a display panel to assess the status of the monitored alarm points. There have existed apparata which were additionally capable of providing limited monitoring of the wiring which connects the alarm contacts to the central monitoring station. Such line monitoring was typically limited to the detection of an "open circuit" in the line. Unfortunately, however, many of such prior art monitoring devices have experienced drawbacks which may make such devices inappropriate for many alarm installations. The line monitoring functions are typically accomplished through the use of additional supervising wiring which is run in parallel with the wiring connecting the remote contact point to the central station. In large scale monitoring environments it is often necessary to monitor many remote points and often these remote points are great distances from the central monitoring station. Accordingly, the additional wire required to supervise the alarm contact line may prove prohibitedly costly forcing the user to go without the added security which a supervised system provides. Furthermore, in many installations, monitoring of the integrity of the wiring for both the occurrence of "open circuits" as well as "short circuits" is mandatory. Accordingly, prior art devices which can only monitor "open" circuits may prove undesireable.
Additionally, in those prior art systems which did implement line monitoring functions, the occurence of a line alarm condition gave no indication as to the type of fault incurred, often requiring that elaborate manual testing of the line be done to locate and correct the fault without the benefit of knowing what type of fault to look for.
Accordingly, it is an object of the present invention to provide a monitoring annunciator apparatus for monitoring the status of field contact points through the utilization of a single signal wire for each monitored contact point and a ground wire common to all monitored contact points to detect the occurrence of a change in status of each monitored field contact point as well as the occurrence of a change in the integrity of each wire pair.
It is additionally an object of the present invention to provide separate audible and visual indication of both the occurrence of a change in status of each monitored field contact point in the form of a contact alarm and indication of the occurrence of a change in the integrity of each wire pair in the form of a line alarm, for each monitored contact point.
It is yet a further object of the present invention to provide such a monitoring annunciator apparatus which may be utilized in environments where a field contact point to be monitored is a great distance from the monitoring annunciator apparatus.
Another object of the invention is to provide for the monitoring of the wiring connecting each field contact point to the monitoring annunciator apparatus for both the occurrence of a "open" circuit and a "short" circuit in an environment in which one wire of the pair is the coimmon ground, with resultant material and labor savings resulting from elimination of respective separate ground wiring.
Yet another object of the present invention is to provide a display panel which will indicate the occurrence of an alarm condition as well as an alarm condition which has been acknowledged but which remains uncorrected.
It is additionally an object of the present invention to provide a monitoring annunciator apparatus having the capability of identifying which particular wire pair is faulty, and further identifying the nature of the fault as either an "open" or a "short" circuit.
These and other objects of the invention will become apparent in light of the present specification and drawings.